The prevalence of migraine is said to be approximately 6% of the male population and 18% of the female population. Treatment for many patients having the occasional migraine usually involves simple analgesics, non-steroidal anti-inflammatory agents, or specific agents such as ergotamines or triptans. Approximately 10% of migraine sufferers have three or more attacks per month and warrant prophylactic treatment. Preventative agents such as beta-blockers, tricyclic antidepressants and divalproex sodium can reduce but not eliminate migraine attacks in some patients. Thus, there remains a need for migraine specific medications such as sumatriptan. In the remaining population of migraine sufferers, and in those with intolerable side-effects from available drugs, there is a lack of conventional pharmaceutical preparations that exhibit therapeutic effect, without severe side-effects.
Droperidol presently is marketed by Akorn, Inc. under the trademark Inapsine, as an injectable formulation used in anesthesia for preoperative surgery. It has never been approved for use in the treatment or management of migraine attacks. The concentration of droperidol in the Inapsine is 2.5 mg/ml. That is the only concentration of droperidol that has been approved for human injection. Further, droperidol is present as the lactate salt in Inapsine. No droperidol salt, other than the lactate, has been used for human injection.
A limited, uncontrolled, non-blinded, use of droperidol lactate (2.5 mg/ml droperidol) to treat migraine attacks was attempted and the results published in Headache, April 1996, p.280. In that publication it was reported that 20 patients received from 2.5 to 7.5 mg droperidol intravenously, in increments of 2.5 mg every 30 minutes until the patient was headache free or until a total of three doses had been administered. All of the patients received prior treatment with migraine therapies. Eighteen of the patients reported to be headache-free by the last dose. Although the article reports on apparently encouraging results in treating migraine attacks with droperidol, no definitive conclusions can be reached from the results reported in that article as the number of patients treated was small, the study was not blinded, all patients received other agents to treat the migraine episode prior to receiving droperidol, and there was no placebo control. Also, there was no attempt to repeat the results with the patients. Further, no attempt was made to prolong therapy beyond the initial treatment to a headache-free state and most patients had continuing symptoms to some degree within 24 hours after the last droperidol treatment.
The study used multiple treatments of droperidol, with many patients receiving more than 2.5 mg of droperidol to reduce the migraine symptoms. The problem with administering droperidol at such a concentration is that the patient receives a significant volume of fluid in order to achieve a therapeutically effective amount of droperidol. This is of particular concern if the patient is receiving the droperidol through intramuscularly (I.M.) injection. Muscle pain and irritation and other problems may be associated with such large fluid injections.